Merge pull request #111 from UCL-CCS/faster_fermionic_ham

Added qubit transformation to Hartree-Fock state builder

symmer/chemistry/build_molecule.py

@@ -2,7 +2,7 @@
 from pyscf.scf.addons import get_ghf_orbspin
 from symmer import QuantumState
 from symmer.symplectic.utils import safe_PauliwordOp_to_dict
-from symmer.chemistry.utils import list_to_xyz, build_bk_matrix
+from symmer.chemistry.utils import list_to_xyz
 from symmer.chemistry import (
     PySCFDriver,
     get_hamiltonian, 
@@ -65,9 +65,7 @@ def __init__(self,
         self.H_q  = get_hamiltonian(self.pyscf_obj.pyscf_hf, qubit_transformation=qubit_transformation)
         self.CC_q = get_coupled_cluster_operator(self.pyscf_obj.pyscf_ccsd, qubit_transformation=qubit_transformation, orbspin=orbspin)
         self.MP_q = get_perturbation_operator(self.pyscf_obj.pyscf_mp2, qubit_transformation=qubit_transformation)
-        self.hf_array = get_hf_state(self.pyscf_obj.pyscf_hf, state_type='array')
-        if self.qubit_transformation in ['bravyi_kitaev', 'BK']:
-            self.hf_array = (build_bk_matrix(self.n_qubits) @ self.hf_array.reshape(-1,1)).reshape(-1) % 2
+        self.hf_array = get_hf_state(self.pyscf_obj.pyscf_hf, state_type='array', qubit_transformation=qubit_transformation)
         self.hf_state = QuantumState(self.hf_array) 
         # build various molecular symmetries
         self.symmetries = get_molecular_symmetries(self.n_qubits, qubit_transformation=qubit_transformation)

symmer/chemistry/molecular_objects.py

@@ -18,7 +18,8 @@
     get_fermionic_up_down_parity_operators,
     get_parity_operators_BK, get_parity_operators_JW,
     array_to_dict_nonzero_indices, 
-    fermion_to_qubit_operator
+    fermion_to_qubit_operator,
+    build_bk_matrix
 )
 
 class PySCFDriver:
@@ -291,7 +292,7 @@ def get_hamiltonian(scf_obj=None,
             fermionic_molecular_hamiltonian += FermionOperator(f'{p}^ {q}^ {r} {s}', coeff*.5)
         return fermionic_molecular_hamiltonian
 
-def get_hf_state(scf_obj, state_type = 'QuantumState'):
+def get_hf_state(scf_obj, state_type = 'QuantumState', qubit_transformation='JW'):
     """
     """
     n_spinorbs = scf_obj.mol.nao*2
@@ -305,6 +306,11 @@ def get_hf_state(scf_obj, state_type = 'QuantumState'):
     hf_array[::2] = np.hstack([np.ones(n_alpha), np.zeros(n_spinorbs//2-n_alpha)])
     hf_array[1::2] = np.hstack([np.ones(n_beta), np.zeros(n_spinorbs//2-n_beta)])
 
+    if qubit_transformation in ['bravyi_kitaev', 'BK']:
+        hf_array = (build_bk_matrix(n_spinorbs) @ hf_array.reshape(-1,1)).reshape(-1) % 2
+    else:
+        assert qubit_transformation in ['jordan_wigner', 'JW',], 'Invaild qubit transformation'
+
     if state_type == 'array':
         return hf_array
     elif state_type == 'QuantumState':